Conventionally, an injection molding machine for molding products made from multiple colors or multiple materials is well known of a type that a turn table is mounted on a moving platen and several moving molds are attached to this turn table as well as the same number of stationary molds are attached to the stationary platen, so that along with the rotation of the turn table, different configurations of cavities are formed one after another by each different combination of the stationary mold and the moving mold, and resin of different colors and materials is successively injected into those cavities. Typical examples of those well known injection molding machines have been disclosed in Japanese Patent Application Laid-Open No. 61-29515 and Japanese Utility Model Application Laid-Open No. 62-53125.
In those conventional injection molding machines, however, positioning of the moving mold and the stationary mold is difficult unless the precision of the rotation and the positioning of the driving mechanism which drives the moving mold is improved. In addition, it is difficult to obtain the products of high reliability when taking aged deterioration into consideration.
And, in the field of molding multiple colors or materials, the general trend is directed toward producing a small quantity of various kinds of goods. In this case, decreasing the expenditure for molds becomes a problem, because the conventional machine is so complicated in its structure and also requires various kinds of high-priced molds, resulting in too much expense for the molds.
Further, the conventional multiple colors or materials molding machine is specialized for multiple colors or materials molding, not for usual one color or material molding. Accordingly, there arises another problem that the adaptability and availability of the molding machine will be deteriorated.
Furthermore, such an injection molding machine is well-known that uses one moving mold in order to decrease the number of molds, as is disclosed in Japanese Patent Application Laid-Open No. 62-152825, a plurality of stationary molds are moved up and down with respect to this one moving mold to establish multiple colors or materials molding. In such a molding machine, however, it is necessary to detach an injection nozzle, which has been inserted into the stationary mold, from the stationary mold by retreating it away from the mold at each time of switching over the stationary mold, thereby causing a prolonged molding cycle; and also there is another defect in that, in case of using an injection nozzle, the resin dripped from the distal end of the nozzle during retraction of the nozzle will be caught between the injection hole of the stationary mold and the nozzle end, so that a gap is defined between the nozzle and the stationary mold. The gap causes the leakage of resin that leads to a break in molding. Although there is such measure to prevent the dripping of resin, as providing a needle valve at the distal end of the nozzle, it presents another problem in that due to the presence of operation mechanism of the needle valve, resin is often stored within the nozzle, which results in the deformity of molding such as burn marks.
One object of the present invention is to provide an injection molding machine for manufacturing products from multiple colors or materials which has a structure so simple as to enable the precise positioning between the moving mold and the stationary mold, as well as the reduction of the expense for the molds.
Another object of the present invention is to provide an injection molding machine for making products of multiple colors or materials which assures the shortening of the molding cycle and also eliminates problems such as the leakage of resin and the like.
Still another object of the present invention is to provide a multiple-functioned injection molding machine which can be used not only for molding products of multiple colors or materials but for molding one color or one material products and also can change colors and resin effectively, as well as it can be applied for multiple-type molding.